This invention relates to a spectrum spread transmitter-receiver adapted to transmit and receive a signal of which a frequency spectrum is spread by a pseudo noise (PN) code, and mere particularly to a spectrum spread transmitter-receiver suitable for use for a remote control device or a radio control device for remotely controlling a garage, an unmanned vehicle in a factory, a crane, illumination of an area, a cargo or the like.
In a spectrum spreading transmitter-receiver, a signal spectrum to be transmitted is spread so as to approximate a spectrum of white noise, whereas in a transmitter, it is decoded by means of correlation; thus, it is considered to be a communication means which is highly resistant to noise. Under the circumstances, it has been conventionally used as a communication means in an environment of increased noise.
Thus, in the spectrum spread transmitter-receiver, a signal is generally spread using a PN code, of which a spectrum resembles white noise, resulting in a band of a base band signal being substantially spread after it has been subjected to modulation.
The base band signal thus spread is used for modulating a carrier, which is then output in the form of a radio wave from an antenna. Subsequently, the output radio wave is received by a receiving antenna and then input to a receiver.
However, such a communication means causes a band of a signal to be substantially spread as described above even when simple information is transmitted, so that a receiver which receives the signal is complicated in structure, leading to an increase in manufacturing cost.
More particularly, as widely known in the art, when a GB product which is a product of gain and an amplifiable band is to be increased, it is necessary to provide an amplifier for this purpose.
Thus, it is also required that a receiver for receiving a signal of a wide band be provided with a specific means for increasing the GB product. Unfortunately, this likewise causes the receiver to be complicated in structure, leading to an increase in manufacturing cost.